In the interest of maximizing thermal efficiency in a standard Steam Methane Reformer (SMR) plant, steam is typically generated from two sources: flue gas waste heat and process heat. This inevitably leads to excess steam generation, more than required internally for the reforming process. In the absence of a steam customer, this results in the last resort measure of installing a steam turbine for realizing economic value.
The concept of supercritical carbon dioxide (S-CO2), as a promising heat extraction working fluid for cool down of nuclear reactors, has been in existence for more than a decade. Most of the technological developments in this area have occurred from a nuclear power perspective. The proof of concept has been well established experimentally. Under the DOE GEN-IV nuclear program, Sandia National lab has developed two small S-CO2 loops (˜1 MW): Compression loop (at Sandia) and Brayton loop (at Barber Nichols). In the past few years, the idea of using S-CO2 cycle for non-nuclear applications has gained traction. Because of a lesser footprint, lower operating and capital costs, it has been proposed to be integrated in solar plants, molten carbonate fuel cells and as first bottoming cycle in combined cycle plants followed by steam as second bottoming cycle. Under the DOE Sunshot initiative (for solar applications), a 10 MWe scale up is currently under development along with industry partners. It is to be noted that for a standard SMR (120 MMSCFD), power generation is ˜19 MW.
In SMR's, for good thermal efficiency purposes, the following ideas have been proposed/implemented. As discussed earlier, installation of a steam turbine to realize economic value out of excess steam. Multiple pre-reformers may be implemented to minimize excess steam. Helical Tube Reactor (HTR) technology has been developed to lower the temperature out of the reformer on the process side.
To date, no prior art exists which advocates the integration of S-CO2 in an SMR in the configuration as proposed herein for significant reduction or, possibly, an elimination of export steam.